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I bought a new LG 34WK95U ultra-wide screen, which has a native resolution of 5120x2160 at 60Hz.

When connecting the monitor via a Thunderbolt 3 USB-C connection, it gets picked up, but it fails to probe for the correct resolution. Also, once connected, I now get two (!) new outputs. Here is my current xrandr:

% xrandr Screen 0: minimum 320 x 200, current 3440 x 1440, maximum 8192 x 8192 eDP-1 connected (normal left inverted right x axis y axis) # Snip; removed the laptop modes DP-1 connected (normal left inverted right x axis y axis) 2560x2160 59.66 640x480 59.94 HDMI-1 disconnected (normal left inverted right x axis y axis) DP-2 connected primary 3440x1440+0+0 (normal left inverted right x axis y axis) 800mm x 330mm 3440x1440 59.97*+ 59.96 49.99 3840x2160 60.00 30.00 1920x1080 60.00 60.00 59.94 1600x900 60.00 1280x1024 60.02 1280x800 59.81 1152x864 59.97 1280x720 60.00 60.00 59.94 1024x768 60.00 800x600 60.32 720x480 60.00 59.94 640x480 60.00 59.94 59.94 5120x2160_60.00 59.99 5120x2160_30.00 29.98 HDMI-2 disconnected (normal left inverted right x axis y axis)

Those DP-1 and DP-2 popped up after I connected the USB-C to the external screen. I am not sure what the meaning of the second output is. Interestingly, when I did this the first time around, DP-1 had all the modes listed, and DP-2 only had those two right now under DP-1.

You can also see the additional modes I added, 5120x2160_60.00 and 5120x2160_30.00 by running % cvt 5120 2160 30 and 60 followed by xrandr --newmode and xrandr --addmode, respectively.

The result of calling xrandr with either of these two modes gives this:

% xrandr --output DP-2 --mode 5120x2160_30.00 xrandr: Configure crtc 0 failed
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  • Guess: USB C alternate mode is not working properly (after all, support is quite new). What computer and what graphic card are you using? At least look into /var/log/Xorg.0.log to find out a bit more what the X server thinks it's doing. But very likely you'll have to file a bug with the USB C alternate mode developers (and if this is on a Mac, getting that to work will be difficult). Commented Dec 6, 2018 at 15:28
  • I seem to have the same issue, just installed Ubuntu 20.04 on a Dell Precision 5540. I could get the full monitor resolution in Windows but on Linux I'm capped at 3440x1440. Did you make any progress, file any bug report somewhere that I can follow? Commented Apr 24, 2020 at 6:03

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I too have the LG 34WK95U monitor. I was able to get my Dell XPS 7590 (OLED) working with an external 4k monitor (HDMI at 30Hz), and the LG at 30Hz via USB-C.

For reference, this is on Ubuntu 20.04.

While the refresh rate certainly isn't ideal, at least the LG resolution is correct now.

Here's what I did:

$ cvt 5120 2160 30 # 5120x2160 29.98 Hz (CVT) hsync: 65.96 kHz; pclk: 452.75 MHz $ xrandr --newmode "5120x2160_30.00" 452.75 5120 5448 5992 6864 2160 2163 2173 2200 -hsync +vsync $ xrandr --addmode DP-1 "5120x2160_30.00" $ xrandr --output DP-1 --mode "5120x2160_30.00"

After running the last command, I did have some overlap of another desktop in one corner. Opening the Settings app and adjusting the monitor layout resolved this.

And the full xrandr output:

$ ~ xrandr Screen 0: minimum 320 x 200, current 8960 x 4320, maximum 16384 x 16384 eDP-1 connected primary 3840x2160+1689+2160 (normal left inverted right x axis y axis) 344mm x 194mm 3840x2160 60.00*+ 59.98 59.97 3200x1800 59.96 59.94 2880x1620 59.96 59.97 2560x1600 59.99 59.97 2560x1440 59.99 59.99 59.96 59.95 2048x1536 60.00 1920x1440 60.00 1856x1392 60.01 1792x1344 60.01 2048x1152 59.99 59.98 59.90 59.91 1920x1200 59.88 59.95 1920x1080 60.01 59.97 59.96 59.93 1600x1200 60.00 1680x1050 59.95 59.88 1600x1024 60.17 1400x1050 59.98 1600x900 59.99 59.94 59.95 59.82 1280x1024 60.02 1440x900 59.89 1400x900 59.96 59.88 1280x960 60.00 1440x810 60.00 59.97 1368x768 59.88 59.85 1360x768 59.80 59.96 1280x800 59.99 59.97 59.81 59.91 1152x864 60.00 1280x720 60.00 59.99 59.86 59.74 1024x768 60.04 60.00 960x720 60.00 928x696 60.05 896x672 60.01 1024x576 59.95 59.96 59.90 59.82 960x600 59.93 60.00 960x540 59.96 59.99 59.63 59.82 800x600 60.00 60.32 56.25 840x525 60.01 59.88 864x486 59.92 59.57 800x512 60.17 700x525 59.98 800x450 59.95 59.82 640x512 60.02 720x450 59.89 700x450 59.96 59.88 640x480 60.00 59.94 720x405 59.51 58.99 684x384 59.88 59.85 680x384 59.80 59.96 640x400 59.88 59.98 576x432 60.06 640x360 59.86 59.83 59.84 59.32 512x384 60.00 512x288 60.00 59.92 480x270 59.63 59.82 400x300 60.32 56.34 432x243 59.92 59.57 320x240 60.05 360x202 59.51 59.13 320x180 59.84 59.32 DP-1 connected 5120x2160+3840+0 (normal left inverted right x axis y axis) 800mm x 330mm 3440x1440 59.97 + 59.96 49.99 3840x2160 60.00 30.00 1920x1080 60.00 60.00 59.94 1600x900 60.00 1280x1024 60.02 1280x800 59.81 1152x864 59.97 1280x720 60.00 59.94 1024x768 60.00 800x600 60.32 720x480 60.00 59.94 640x480 60.00 59.94 5120x2160 59.99 5120x2160_30.00 29.98* DP-2 connected (normal left inverted right x axis y axis) 2560x2160 59.66 640x480 59.94 DP-3 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 697mm x 392mm 3840x2160 30.00* 25.00 24.00 29.97 23.98 2560x1440 59.95 2048x1280 59.99 2048x1080 24.00 1920x1080 60.00 60.00 50.00 59.94 25.00 24.00 23.98 1920x1080i 60.00 50.00 59.94 50.00 1600x1200 60.00 1600x900 60.00 1280x1024 75.02 60.02 1152x864 75.00 1280x720 60.00 50.00 59.94 1024x768 75.03 60.00 800x600 75.00 60.32 720x576 50.00 720x480 60.00 59.94 640x480 75.00 60.00 59.94

Ideally this should be supported out of the box. But the 5120x2160 resolution isn't recognized by default in Gnome Settings. Hopefully this information helps someone else!

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I faced similar problems when trying to connect an LG 34WK95U-W 5120x2160 to my Asus Zenbook S UX393EA on Pop OS 20.10. Problem was solved after updating kernel to 5.10. System now runs 5120x2160 @ 60 Hz.

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